Speed up identifier, keyword and smi parsing

src/scanner.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_SCANNER_H_
 #define V8_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 547 matching lines @@
     next_.literal_chars = NULL;
     next_.raw_literal_chars = NULL;
   }
 
   inline void AddLiteralCharAdvance() {
     AddLiteralChar(c0_);
     Advance();
   }
 
   // Low-level scanning support.
-  template <bool capture_raw = false>
+  template <bool capture_raw = false, bool check_surrogate = true>
   void Advance() {
     if (capture_raw) {
       AddRawLiteralChar(c0_);
     }
     c0_ = source_->Advance();
+    if (check_surrogate) HandleLeadSurrugate();
+  }
+
+  void HandleLeadSurrugate() {
     if (unibrow::Utf16::IsLeadSurrogate(c0_)) {
       uc32 c1 = source_->Advance();
       if (!unibrow::Utf16::IsTrailSurrogate(c1)) {
         source_->PushBack(c1);
       } else {
         c0_ = unibrow::Utf16::CombineSurrogatePair(c0_, c1);
       }
     }
   }
 
@@ skipping 164 matching lines @@
   bool harmony_classes_;
   // Whether we scan TEMPLATE_SPAN and TEMPLATE_TAIL
   bool harmony_templates_;
   // Whether we allow \u{xxxxx}.
   bool harmony_unicode_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_H_